Field of the Invention
The present invention relates to an imaging apparatus and an imaging system.
Description of the Related Art
In imaging apparatus such as complementary metal oxide semiconductor (CMOS) image sensors, there is a demand for a faster imaging process. Therefore, a faster process is demanded also in an amplifier circuit used in an imaging apparatus. One technique for performing a faster amplification process in an amplifier circuit is to increase the output slew rate of an amplifier circuit.
G. Nicollini, F. Moretti, and M. Conti, “High-frequency fully differential filter using operational amplifiers without common-mode feedback”, IEEE Journal of Solid-State Circuits, vol. 24, no. 3, pp. 803-813, June 1989 discloses a differential amplifier circuit in which a bias current of a second differential input stage is increased by the output of a first differential input stage resulting in an increased slew rate of the output of the second differential input stage.
In the differential amplifier circuit of the above document, however, a large bias current is always supplied thereto involving large power consumption. As discussed above, a larger slew rate of an amplifier circuit tends to cause increased power consumption. Therefore, in increasing the speed of an imaging apparatus, one of the objects will be to achieve lower power consumption along with an increased speed.